The present invention relates to oral care compositions containing a solubilized and uniformly dispersed antioxidant. In particular, the antioxidant is ubiquinone (2,3-dimethoxy-3-methyl-6-decaprenyl-1,4-benzoquinone) otherwise designated, Coenzyme Q.sub.10. Coenzyme Q.sub.10 is a potent water insoluble antioxidant that is involved in electron transport and oxidative phosphorylation.
Oral care compositions include solutions, emulsions and devices that help maintain healthy teeth and gums for use by individuals and by dental professionals. These compositions include toothpastes, tooth gels, mouth rinse, oral sprays, pastes, ointments, films, dental gels, irragants, dental floss, and other related products that are designed for the maintenance and care of the oral cavity.
It is generally accepted that compositions designed to deliver an active substance, for example a drug, to a given tissue are more effective when the substance is solubilized and dispersed in a uniform manner. In the formulation of oral care compositions which are designed to last in the oral cavity for short periods of time, the availability of an active ingredient is particularly important. For example, toothpastes are generally used for less than two minutes for cleaning teeth. The delivery of active oral care ingredients, such as sodium fluoride, must be formulated in a manner to reach the desired target, e.g., teeth and gums, before it is removed from the oral cavity.
Dental studies in humans have demonstrated a deficiency of Coenzyme Q.sub.10 in the gingiva tissues of individuals with gum disease (Littaru et al., Proc. Natl. Acad. Sci. USA 68:2332-2335 (1971), Nakamura et al., Int. J. Vit. Natr. Res. 43:84-92 (1973)). Clinical studies have shown that dietary supplementation with orally ingested formulations of Coenzyme Q.sub.10 improved diseased gingiva tissues in adult humans (Wilkinson et al., Res. Comm. Chem. Path. Pharm. 13:715-719 (1976), Folkers, J. Dent. Health 42:258-263 (1992)). Also, a decrease in sub-gingival microbes has been observed following oral supplementation of Coenzyme Q.sub.10 (McRee et al., J. Dent. Health 43:659-666 (1993)). These systemic formulations provide relatively low concentrations of Coenzyme Q.sub.10 to the gingival tissues.
Coenzyme Q.sub.10 has also been formulated as an oral care product to treat gingivitis. In one formulation, Coenzyme Q.sub.10 was compounded for topical application in soybean oil. The composition was applied to periodontal pockets of receding gums by a dentist. In these studies there was an improvement in periodontal condition (Hanioka et al., Mol. Aspects. Med. 15:241-248 (1994).
Recently, oral care compositions comprising Coenzyme Q.sub.10, including a toothpaste, have been disclosed in Swedish Patent publication No. 9500610-2. In these compositions soybean oil at about 2% was used as a solubilizing and encapsidizing agent. It has been determined that this amount of oil provides a product with unfavorable consumer characteristics, including an unattractive feel and taste.
In another formulation for an oral care product, Coenzyme Q.sub.10 was combined with a protective colloid forming substance. The colloid forming substance was provided to protect the Coenzyme Q.sub.10 from breakdown and to release the coenzyme upon contact with the environment of the oral cavity. As oral care compositions are present in the oral cavity for relatively brief periods of time. The time period required for release of the coenzyme from the colloid forming substance can reduce the amount of active coenzyme available to the gingiva.
It is common in the art when formulating oral care compositions to solubilize water-insoluble ingredients, e.g., Coenzyme Q.sub.10, in natural essential oils used to flavor the composition. Commonly used oils include, for example, peppermint oil, spearmint oil, and the like. When formulated in this way the maximum quantity of water-insoluble ingredient which can be in the formulation is limited by the solubility of the ingredient in the essential oil. For example we have found that the higher concentration of Coenzyme Q.sub.10 that can be added to the essential oil in the preparation of a toothpaste is about 0.05%. If a greater concentration of the ingredient is added, the product becomes unstable and the water-insoluble ingredients can precipitate or separate from the composition.
Previous oral care compositions have solubilized Coenzyme Q.sub.10 in lipids, e.g., soybean oil, flax or bran seed oil, and the like in order to increase the amount Coenzyme Q.sub.10 which can be added. The inherent oily characteristics of these formulations provides a commercial product having unfavorable consumer reaction. For example, in toothpaste, the high concentrations of, for example, soybean oil required to solubilize and encapsidize sufficient concentrations of Coenzyme Q.sub.10 to be effective in treating or ameliorating the symptoms of gingivitis or periodontitis can provide a composition having an oily taste and feel in the oral cavity. Also, toothpaste preparations comprising high concentrations of oil can have a tendency to separate.
The tendency of water and oil phases of certain oral care formulation to separate can also be disadvantageous when an oral care composition is formulated as a mouth rinse, oral spray, dental gel or other formulation including a base composition for use in the coating used with dental floss or toothpicks. When formulated as a mouthwash, phase separation can occur such that the oil phase containing the Coenzyme Q.sub.10 floats on top of the aqueous solution at a concentration of one or more parts per million. Solubilizing Coenzyme Q.sub.10 in oil for the preparation of dental floss or a toothpick can result in a product which is oily to the taste and feel.
Surprisingly, the present invention provides compositions and methods for incorporating high concentrations of Coenzyme Q.sub.10 which are effective to improve the condition of gingival tissues in oral care formulations without the problems of oil/water phase separation and without providing compositions which possess unfavorable taste and tactile characteristics.